The chloride method for producing titanium dioxide (“TiO2”) consists of reacting preheated oxygen gas with titanium tetrachloride (“TiCl4”) gas to produce TiO2 particles. Additives in small amounts can be used to control the particle size and structure. Hydrocarbon fuel can be added to the preheated oxygen to increase its temperature further to a final oxygen temperature of about 3000° F. to about 3800° F. prior to the reaction with titanium tetrachloride vapor. The use of supplemental hydrocarbon fuel eliminates the need to build a hot oxygen supply system that can withstand the elevated temperatures that are required.
Hydrocarbon fuels either in the vapor phase or in the liquid phase can be used to increase the oxygen temperature to its final temperature during the TiO2 production process. There exist advantages to using hydrocarbon fuels in the liquid phase. These advantages include, for example, a safer means to deliver the fuel to the reaction zone, the use of low-grade, less costly fuel, and the ability to deliver additives to the reaction zone in a consistent manner by dissolving the additives in the fuel.
However, problems often arise when using liquid fuel injection systems in the production of TiO2. For example, the fuel has to be injected into the hot gas stream in such a way that the heat from the combustion of the fuel does not destroy the injection nozzles or the reactor walls. Additionally, when the system shuts down, an immediate purge of the fuel lines is required to protect the nozzles, as well as prevent pyrolysis of the hydrocarbon fuel in such lines. If the fuel pyrolyzes, solid carbon particles can be produced that block the fuel lines and the fuel delivery system can become unusable.
The present invention provides for liquid fuel injectors that allow the injection of a fine spray of liquid fuel. Liquid fuel injectors of the present invention utilize a schrader valve movable between an open position and a closed position. When the schrader valve is in the closed position fuel flow is blocked and purge gas is allowed to flow through the fuel injectors. When the schrader valve is in the open position, the flow of purge gas is blocked and fuel is allowed to flow through the fuel injector. In this manner, the fuel injectors of the present invention provide for an immediate and automatic purge of the fuel lines when the fuel flow is shut off.